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We propose an implementation of the PCD technique to minority carrier effective lifetime assessment in crystalline silicon at 77K. We focus here on (n)-type, FZ, polished wafers passivated by a-Si:H deposited by PECVD at 200°C. The samples were immersed into liquid N2 contained in a beaker placed on a Sinton lifetime tester. Prior to be converted into lifetimes, data were corrected for the height shift induced by the beaker. One issue lied in obtaining the sum of carrier mobilities at 77K. From dark conductance measurements performed on the lifetime tester, we extracted an electron mobility of 1.1x104 cm².V-1.s-1 at 77K, the doping density being independently calculated in order to account for the freezing effect of dopants. This way, we could obtain lifetime curves with respect to the carrier density. Effective lifetimes obtained at 77K proved to be significantly lower than at RT and not to depend upon the doping of the a-Si:H layers. We were also able to experimentally verify the expected rise in the implied Voc, which, on symmetrically passivated wafers, went up from 0.72V at RT to 1.04V at 77K under 1 sun equivalent illumination.
The death of patients treated by ventricular assist device is usually related to multiorgan failure for which a disorder of splanchnic circulation is blamed. Gastric tonometry (measurement of gastric intra-mucosal pressure of CO2) has already been studied in many fields and especially in cardiac surgery. The aim of this study was to investigate the prognostic value of gastric tonometry monitoring after implantation of a ventricular assist device.
In this prospective study, all consecutive patients scheduled for a ventricular assist device were included. Gastric tonometry was added to standard monitoring. Data were collected (lactate, gastric CO2 (PgCO2) during cardiopulmonary bypass, at admission to ICU, 24 and 48 h later and when norepinephrine was stopped. Preoperative biologic and haemodynamic data were also collected. The primary endpoint was death.
Fifty-six patients (50 men and 6 women) were included. In 91% of the cases, the mechanical assistance was biventricular. The objective of the assistance was a bridge to transplant in 93% (n = 27). Twenty-seven deaths (48%) occurred during the study, 59% (n = 16) of them took place before the cardiac transplantation (mean time = 18 ± 16 days after assist device insertion). Many factors were found to be associated with death: weight (P = 0.018), red cells administration (P = 0.025), length of surgery (P = 0.016), PgCO2 on admission to ICU (P = 0.040) and norepinephrine dose at 24 h.
Gastric tonometry has a prognostic value in the early postoperative hours after the implantation of a ventricular assist device.
Arterial pulse waveform analysis has been proposed for cardiac output (CO)
determination and monitoring without calibration or thermodilution
(FloTrac™/Vigileo™; Edwards Lifesciences, Irvine, CA,
USA). The accuracy and clinical applicability of this technology has not
been fully evaluated. We designed this prospective study to compare the
accuracy of the FloTrac™ system (COFT) vs. pulmonary
artery catheter standard bolus thermodilution (COPAC) in patients
undergoing coronary artery bypass grafting.
We studied 11 patients referred for coronary artery bypass grafting.
COFT and COPAC were determined at six time points
in the operating room including before and 5 min after volume expansion (500
mL 6% hetastarch). Measurements were performed on arrival in the intensive
care unit and every 4 h afterwards. Bland–Altman analysis was
used to assess the agreement between COFT and
COPAC ranged from 2.0 to 7.6 L min−1 and
COFT ranged from 1.9 to 8.2 L min−1.
There was a significant relationship between COPAC and
COFT (r = 0.662; P < 0.001). Agreement between
COPAC and COFT was −0.26 ±
0.87 L min−1. Volume expansion induced a significant
increase in both COPAC and COFT (from 3.4 ±
0.8 to 4.4 ± 1.0 L min−1; P < 0.001 and from 3.9 ±
1.2 to 5.0 ± 1.1 L min−1; P < 0.001, respectively) and there
was a significant relationship between percent change in COPAC
and COFT following volume expansion (r = 0.722; P = 0.01).
We found clinically acceptable agreement between COFT and
COPAC in this setting. This new device has potential clinical
After a quick tour of polarization basics, I review interstellar polarization starting
with its galactic distribution, and then going into molecular clouds. The properties of
interstellar polarization are discussed, its wavelength dependence and the 3 parameters
used to specify it. Then more recent work since approximately the last 15 years which
show significant deviations from the usual behavior in the densest regions of molecular clouds
is presented. Recent results for two specific regions are presented, and finally I conclude
by summarizing the main points.
Even a brief glance at astronomical journals indicates the breadth and depth of observational projects making use of photometric and polarimetric techniques. Examples of ongoing photometric and polarimetric research as related by Commission Members follows. I thank the Commission Members, acknowledged below, for their input.
The value of 2 PCR methods, targeting genomic and kinetoplast minicircle DNA respectively, was investigated for both diagnosis and prevalence studies of canine visceral leishmaniasis (CVL). The first method (R) was 5000-fold less sensitive than the second (method KRV). Both were tested for diagnosis of CVL in 44 sick dogs with confirmed disease using different biological samples. Method R was highly efficient when using invasive samples, but the use of method KRV proved necessary for a 100% sensitive diagnosis using peripheral blood. This method was applied to peripheral blood and skin samples in 263 dogs during a mass survey in the Cévennes focus. PCR was compared to serology and all results were analysed according to clinical status. The ‘CVL-infection’ prevalence was found to be 79.8% by PCR compared with 29.6% by serology: 89.4% of symptomatic and 65.2% of asymptomatic dogs harboured parasites in peripheral blood. This study confirms the high prevalence of asymptomatic carriers of Leishmania. In total, for the diagnosis of CVL in sick dogs, method R is recommended in view of its 100% positive predictive value (compared with 30% for method KRV). A strategy best adapted for prevalence surveys might combine serology and highly sensitive PCR on peripheral blood.
In Figure 1, we present a map of the polarization of background starlight in the Perseus region (Goodman, Bastien, Myers, and Menard 1989) superposed on contours of integrated 13CO emission (Bachiller and Cernicharo 1986). The polarization vectors map the plane-of-the-sky field (B⊥), assuming as usual that the observed polarization is the result of selective extinction by magnetically aligned dust grains associated with the molecular clouds between the observer and background stars (e.g. Dolginov 1989).
During the course of a monitoring programme of the linear polarization of various T Tauri stars, UY Aur was observed to undergo a strong polarization burst between 1984 October and 1985 January. The linear polarization rised from about 1.5% early in 1984 to a maximum of 7.6% in 1984 October and declined back to the earlier value after 3 to 4 months. It is the first time that such a large increase in linear polarization is reported in a T Tauri star. However the interpretation is complicated by the fact that UY Aur is a visual binary with a separation of 0.8 and both components were included in the measurements.